Hi,

Well, quite a bit actually. The problem with points was that they had to switch a good bit of current very rapidly and would thus wear out. All 12 volt car systems I'm aware of actually started on 12 volts, then ran through a resistor to cut the power down to 6 volts for running, in an effort to make the points last longer. Eventually, someone figured out that they could design a transistor switching circuit to turn the power off and on like the points, but without the wear and tear. This could be done with a magnetic sensor setup, an optical setup using an LED, or with the Hall Effect sensor, and a simple transistor circuit. This is the Kettering system, how so ever it is switched.

It didn't take them long to figure from there, that this could be taken further to overcome a limitation of points; that is that they didn't like to switch a lot of power without burning up too quickly. More in is more out of the coil, so by using a capacitor circuit along with the aforementioned sensor and transistor switching, they could step up the current through the coil and get a hotter spark. This capacitor is charged, and circuited to discharge through the coil at a higher current and a hotter spark is the end result. The actual benefit of this is generally seen in poor conditions such as a fouled plug, etc. Then the CD ignition definitely out performs the other systems.

As far as I know, the CD systems are not dwell sensitive like the Kettering systems. I will be talking to CH ignitions tomorrow, and I'm going to ask them about this. I'll let you all know if I find out anything new.

By the way; with any of these electronic ignitions systems, a person could rig up two Hall Effect sensors for different timing through a switch. You would not have the smooth transition of the variable timing systems, but it might be the answer for some whom are having a problem with the prop biting them, and would like to just retard the ignition to start the engine.

Hope this all helps,
Thanks,
AV8TOR